Gas-heated cooking surfaces for gas stoves and heating members have been described in German Offenlegungsschrift 24 40 701.0-16 or in U.S. Letters Patent No. 3,494,350. In these printed publications, infrared radiation burners have been described in diverse embodiments which are principally suitable for heating glass-ceramic cooking surfaces. Particularly in the German Offenlegungsschrift No. 24 40 701.0-16, a gas stove with one or more cooking station burners is described wherein each burner is constructed in the form of a gas-heated radiation burner; that is, in the form of a burner subassembly in which the gas undergoes flameless combustion on the surface of perforated ceramic plate, and wherein, at a distance above each burner's ceramic plate, there is arranged a common glass-ceramic plate of a type which is known as such to the prior art. The space surrounding the burners is dimensioned to be of such a size that it takes up the combustion gases flowing laterally off from the periphery of the burners. Combusted gases can be freely emitted at openings which are located outside the glass ceramic plate and which are disposed at points removed from the working surface of the gas stove, but this space is otherwise closed on all sides. Each of the radiation burners is here provided with an ignition device and an ignition safety device to protect against a combustible gas mixture flowing off which has not been combusted.
Although gas-heated radiation burner subassemblies such as this are principally intended for stoves, or heating surfaces, the complicated nature of such heating systems results in considerable difficulties in the practical application of these prior art burners in connection with glass ceramic cooking surfaces. The specific problems consist in the circumstance that, while the glass ceramic cooking surface must be protected against overheating, and an adequate ignition safeguard must be maintained, the start-up cooking times must be short, the efficiency must be great, and the possibility of a good heat energy regulation must be provided. The combustion temperature of a burner's gas flame, or the temperature of the radiating ceramic plate associated with such an infrared-radiation burner, respectively, must amount to more than 900.degree. C. for a good transmission of radiation. On the other hand, in order to ensure a good transmission of heat, the distance between the radiating ceramic plate and a cover plate must be as small as possible.
The permissible maximum temperature of such known common glass ceramic-cooking surfaces normally lies at about 700.degree. to 750.degree. C. When the pots used in cooking are good and have a flat bottom surface, this temperature is not exceeded even in the case of the above radiation temperature, since a good heat transmission takes place. However, when poor pots with non-flat bottom surfaces are used, or when there are extreme loads such as, for example, in the case of a pot whose contents have been cooked away, temperatures of more than 900.degree. C. can occur on and in the glass ceramic-heating surface in only a few minutes. These possible but excessive temperatures must be reliably prevented by a temperature limiting device. The difficulty in this regard lies in the fact that, if the limiting device is inexpediently located or constructed, the start-up cooking times are unduly prolonged, and the limiting device functions in a non-constant manner, depending upon such variables as the type of pot used, the load applied to the cooking surface, and the like.
The practical situation involving the heating a cooking surface requires, in addition to such a temperature limiting device, the capability of a sensitive adjustment for achieving the most diverse energy stages or gradations through the operation of a suitable control device for the greatest possible variety of pots and foods cooked, whereby the limitation of a maximum usable temperature, as well as short start-up cooking times, are to be included as reasonable objectives. A sensitive regulating device with such characteristics that take into account the greatest possible variety of cooking utensils, presents great difficulties in fabricating in the case of the presently known gas-heated glass ceramic cooking surfaces.
A gas stove is described in the German Offenlegungsschrift 24 40 701.0-16, wherein one or more cooking location-radiation burners are located beneath a glass ceramic-cooking surface. The waste or combusted gas from these burners is taken into by a common, sufficiently large space between the burner(s) and the glass ceramic cooking surface plate, and is subsequently discharged at the rear of the stove. This embodiment is apparently suitable for heating the cooking surface. However, considerable difficulties in the precise energy control, as well as in the limitation of the maximum temperature of each individual cooking zone, result due to the fact that the plurality of burners used mutually influence one another as a consequence of the freely flowing exhaust gases. Moreover, this common exhaust gas space between the individual burners results in an additional partially heated space, as a consequence of which it is not possible to maintain precisely defined cooking zones.
The arrangement of the various elements employed for energy regulation, temperature limitation, ignition, and ignition safeguard must be established for each respective type of gas stove being manufactured, and since the size of the glass-ceramic-cooking surface and the arrangement of the individual burners needs to be varied from one gas stove type to another, there are consequently problems regarding construction and production, in addition to the considerable assembly costs involved in prior art stoves of this class.